In this article an original method for automatic generation of CAD models affected by shape errors is described. The model is suited for the generation of a random error conditioned by some requirements. In order to analyse the possibility to control the main characteristics of the geometric error, some experiments has been conducted for different values of the model parameters. The results of these experiments have been used to define a function that correlates the model parameters with the technical parameters. The proposed method can be used in the analysis of industrial applications where the shape error affects the product functionality. A promising utilisation is in Monte Carlo simulations to generate the instances to be analysed.